Gas detectors

Abstract

Apparatus for determining the concentration of a component of a gaseous mixture by selective absorption of the component in a liquid absorbent and measurement of a property of the absorbent, such as the electrical conductivity, related to the concentration of the component therein, comprising an absorption cell for containing the liquid absorbent; means for bringing a stream of said gaseous mixture into contact with the absorbent; means for flushing the absorption cell with absorbent from a reservoir so as to recharge the cell with absorbent; and means for providing a first signal related to said property of the absorbent immediately after flushing the cell, for providing a second signal related to the property after a predetermined time, and for providing a third signal related to the difference between the second and first signals.

We claim: 
     
       1. Apparatus for determining the concentration of a component of a gaseous mixture by selective absorption of the component in a liquid absorbent and measurement of a property of the absorbent related to the concentration of the component therein, the apparatus comprising an absorption cell for containing the liquid absorbent; means for bringing a stream of said gaseous mixture into contact with the absorbent; means for flushing the absorbent cell at regular intervals of time with absorbent from a reservoir so as to recharge the cell with absorbent; means for returning the absorbent flushed from the cell to the reservoir; and means for providing a first signal related to said property of the absorbent immediately after flushing the cell, for providing a second signal related to said property immediately before flushing the cell in the next interval of time, and for providing a third signal related to the difference between the second and first signals. 
     
     
       2. Apparatus according to claim 1 in which the means for bringing a stream of the gaseous mixture into contact with the absorbent comprises a jet-forming means arranged to direct a jet of the gaseous mixture on to the surface of the absorbent. 
     
     
       3. Apparatus according to claim 1 in which the property of the absorbent related to the concentration of the component therein is the electrical conductivity. 
     
     
       4. Apparatus according to claim 1 further comprising temperature sensitive means arranged to sense the temperature of the absorbent and to compensate the first and second signals in accordance with the sensed temperature. 
     
     
       5. A method of determining the concentration of a component of a gaseous mixture by selective absorption of the component in a liquid absorbent and measurement of a property of the absorbent related to the concentration of the component therein, comprising bringing a stream of gaseous mixture into contact with a quantity of said absorbent in an absorption cell; flushing the absorption cell with absorbent from a reservoir so as to recharge the cell with absorbent; returning the absorbent flushed from the cell to the reservoir; providing a first signal related to said property of the absorbent immediately after flushing the cell, providing a second signal related to the property immediately before flushing the cell in the next interval of time, and providing a third signal related to the difference between the second and first signals.